Signal-Android/app/src/main/res/layout/mentions_picker_fragment.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:clipChildren="false">

    <FrameLayout
        android:id="@+id/mentions_picker_bottom_sheet"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:behavior_peekHeight="216dp"
        app:layout_behavior="com.google.android.material.bottomsheet.BottomSheetBehavior">

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/mentions_picker_list"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
            android:background="@color/signal_colorSurface1" />

    </FrameLayout>

</androidx.coordinatorlayout.widget.CoordinatorLayout>